Ionic liquid-catalyzed alkylation of isobutane with 2-butene

1H, 13C, 15N NMR, and DFT Studies on Complex Formation of Zinc(II) Ion with Ethylenediamine in Ionic Liquid [C2mIm][TFSA]

In bis(trifluoromethylsulfonyl)amide (TFSA-)-based ionic liquid (IL), 1-ethyl-3-methylimidazolium TFSA- ([C2mIm][TFSA]), the complex formation equilibria of zinc(II) ion (Zn2+) with ethylenediamine (EN) have been investigated. An EN molecule may coordinate with Zn2+ as a bidentate ligand. First, the formation of Zn2+-EN complexes in [C2mIm][TFSA] was confirmed from the difference of 1H and 13C NMR chemical shift values of EN molecules between [C2mIm][TFSA]-EN binary solvents and the 0.1 mol dm-3 Zn(TFSA)2/[C2mIm][TFSA]-EN solutions as a function of EN mole fraction xEN. Second, the stability constants of Zn2+-EN complexes formed in the IL were determined from the concentration ratio [EN]/[Zn2+] dependence of 15N NMR chemical shift values of the TFSA- N atom in the Zn2+/IL-EN solutions. In the IL, mono-, bis-, and tris-EN complexes are successively formed by 1:1 replacement of TFSA- anions coordinated with Zn2+ by EN molecules with increasing EN content. Third, 1H and 13C NMR measurements with the help of density functional theory (DFT) calculations were made on [C2mIm][TFSA]-EN binary solvents as a function of xEN to clarify key interactions to the mechanism of the complex formation. Fourth, the stability constants of Zn2+-EN complexes in the IL were compared with those in aqueous solutions. It was suggested that the hydrogen bonding of the EN molecule with the imidazolium ring H atoms and the TFSA- O atoms reduces the stability of the mono-EN complex in the IL. In contrast, the intracomplex hydrogen bonds between EN and TFSA- in the first coordination shell contribute to the higher stability of the bis-EN complex in the IL than that in aqueous solutions. The difference in the stability constants between the tris-EN complexes and hexaacetonitrile complexes, where acetonitrile (AN) molecules act as monodentate ligands, was interpreted in terms of the higher electron donicity of EN. Finally, to verify the present evaluation, the experimental 13C NMR chemical shift values of EN molecules in the solutions were compared with the theoretical values calculated by DFT using the stability constants determined.

Enabling Sustainable Chemistry with Ionic Liquids and Deep Eutectic Solvents: A Fad or the Future?

Ionic liquids (ILs) and deep eutectic solvents (DESs) debuted with a promise of a superior sustainability footprint due to their low vapor pressure. However, their toxicity and high cost compromise this footprint, impeding their real-world applications. Fortunately, their property tunability through a rational selection of precursors, including bioderived ones, provides a strategy to ameliorate toxicity, lower cost, and endow new functions. This Review discusses whether ILs and DESs are sustainable solvents and how they contribute to sustainable chemical processes.

Kinetic Model of Olefins/Isobutane Alkylation Using Sulfuric Acid as Catalyst

The alkylation of isobutane and low molecular olefins using strong acid as catalysts is an important process in the petrochemical field, and its product, alkylate, is an ideal gasoline blending component due to high octane number, low vapor pressure, low sulfur, and lack of aromatics. To better meet the optimization process of the simulation of the alkylation unit, a reaction kinetic model with 20 reactions based on industrial data was developed, in which the alkylation products were divided into lumped components in detail. The reactor model was established based on the flow state and structural pattern of the industrial reactor, considering the internal circulation flow, and is suitable for the simulation of the DuPont alkylation process. Also, eventually, the model parameters were solved by the nonlinear least-squares fitting method. The results of the validation calculations showed that the kinetic model fitted the experimental data with good agreement. In addition, the reaction kinetic model was used to predict the influence of operating conditions, which is consistent with the trend in actual industrial production.

Effects of Cu(I) contents on voltammetric behavior and electrodeposition mechanism of bimetallic composite ionic liquids

Effective electrochemical recovery of metal for bimetallic composite ionic liquid (IL) is related to ion species and even the reaction mechanism under different Cu(I) content, thus bimetallic composite ILs (Et3NHCl-1.54AlCl3-xCuCl,...

POSS and imidazolium-constructed ionic porous hypercrosslinked polymers with multiple active sites for synergistic catalytic CO2 transformation

In this work, we reported a facile one-pot approach to construct polyhedral oligomeric silsesquioxane (POSS) and imidazolium-based ionic porous hypercrosslinked polymers (denoted as iPHCPs) with multiple active sites towards efficient catalytic conversion of carbon dioxide (CO₂) to high value-added cyclic carbonates. The targeted iPHCPs were synthesized from a rigid molecular building block octavinylsilsesquioxane (VPOSS) and a newly-designed phenyl-based imidazolium ionic crosslinker through the AlCl₃-catalyzed Friedel-Crafts reaction. The desired multiple active sites come from the mixed anions including free Cl^- and Br^- anions, and in situ formed Lewis acidic metal-halogen complex anions [AlCl₃Br]^- within imidazolium moieties and POSS-derived Si-OH groups during the synthetic process. The typical polymer iPHCP-12 possesses a hierarchical micro-/mesoporous structure with a high surface area up to 537 m² g^-1 and shows a fluffy nano-morphology. By virtue of the co-existence of free nucleophilic Cl^- and Br^- anions, the metal complex anion [AlCl₃Br]^- with both electrophilic and nucleophilic characters and electrophilic hydrogen bond donor (HBD) Si-OH groups, iPHCP-12 is regarded as an efficient recyclable heterogeneous catalyst for synergistic catalytic conversion of CO₂ with various epoxides into cyclic carbonates under mild conditions. The present work provides a succinct one-pot strategy to construct task-specific ionic porous hypercrosslinked polymers from easily available modules for the targeted catalytic applications.

Synthesis of Alkylbenzene from Medium-Chain Olefins Catalyzed by an Acidic Ionic Liquid and the Surface Properties of Their Sulfonate

The Fischer-Tropsch synthesis can be used to achieve a high content of α-olefin (C5–C11) products using Fe-based catalysts. Herein, C6 and C8 α-olefins have been selected as examples for the alkylation of benzene catalyzed by using an acidic ionic liquid (Et3NHCl-AlCl3) to obtain a variety of intermediates used to prepare surfactants. A series of alkylbenzenes were synthesized by controlling the reaction conditions and their corresponding alkylbenzene sulfonates were successfully obtained by sulfonation and neutralization. It was found that the single chain alkylbenzene sulfonate derivatives did not display typical surfactant properties due to their short hydrophobic chain length. However, double chain alkylbenzene sulfonates exhibit excellent surfactant properties, and decrease the water surface tension compared to commercially available sodium dodecylbenzene sulfonates. A γ cmc (mN m−1) value of 32.70 was observed for sodium di-hexylbenzene sulfonates, 29.98 for sodium di-octylbenzene sulfonates, and 36.0 for sodium dodecylbenzene sulfonates. In addition, double chain alkylbenzene sulfonates show an improved emulsifying and wettability performance compared to sodium dodecylbenzene sulfonate. This demonstrates that the capability of alkylbenzene sulfonate to decrease the surface tension are closely related to the total carbon number of side chain-alkyl groups connected to the benzene ring.

Cold model investigation of mixing-separation time distribution in a multi-element process coupled cyclone reactor for ionic liquid-catalyzed isobutane/butene alkylation

The residence time distributions of a dispersed phase in a multi-element process coupled cyclone reactor for ionic liquid-catalyzed isobutane/butene alkylation were numerically studied with a CFD method. The Eulerian-Eulerian multiphase flow model and Reynolds stress model were applied to simulate the flow field distribution in the cyclone reactor. The time in which the dispersed phase flows from the inlet slot to the overflow outlet tube is defined as the mean mixing-separation time between two phases in the cyclone reactor. The effects of the structural parameter of the slot on the mean mixing-separation time were investigated in this work. The results show that the residence time distributions are unimodal except for the condition that the number of slots is 1. Besides, it is concluded that the velocity of dispersed phase flow into the reaction chamber and the relative velocity between two phases in the cyclone reactor are the main influence factors. Based on the results, a prediction model to explain the relationship between the mean mixing-separation time and the velocity of two phases was established.

Mixed Chlorometallate Ionic Liquids as C4 Alkylation Catalysts: A Quantitative Study of Acceptor Properties

The acceptor properties of mixed chlorometallate ionic liquids for isobutane-butene alkylation (C4 alkylation) reaction were studied. These ionic liquids were prepared by mixing metal chlorides with either triethylamine hydrochloride or 1-butyl-3-methylimidazolium chloride in various molar ratios. Using triethylphosphine oxide as a probe, Gutmann Acceptor Numbers (AN) of the catalysts were determined, and the Lewis acidity of mixed chlorometallate ionic liquids was quantitatively measured. Additionally, AN value was developed to determine the relationship between Lewis acidity and catalytic selectivity. The favorite AN value for the C4 alkylation reaction should be around 93.0. The [(C2H5)3NH]Cl–AlCl3−CuCl appears to be more Lewis acidity than that of [(C2H5)3NH]Cl–AlCl3. The correlation of the acceptor numbers to speciation of the mixed chlorometallate ionic liquids has also been investigated. [AlCl4]−, [Al2Cl7]−, and [MAlCl5]− (M = Cu, Ag) are the main anionic species of the mixed chlorometallate ILs. While the presence of [(C2H5)3N·M]+ cation always decreases the acidity of the [(C2H5)3NH]Cl−AlCl3−MCl ionic liquids.

Isobutane/2-butene alkylation catalyzed by Brønsted–Lewis acidic ionic liquids

The alkylation reaction of isobutane with 2-butene to yield C₈-alkylates was performed using Brønsted–Lewis acidic ionic liquids (ILs) comprising various metal chlorides (ZnCl₂, FeCl₂, FeCl₃, CuCl₂, CuCl, and AlCl₃) on the anion. IL 1-(3-sulfonic acid)-propyl-3-methylimidazolium chlorozincinate [HO₃S-(CH₂)₃-mim]Cl-ZnCl_{2 (x=0.67)} exhibited outstanding catalytic performance, which is attributed to the appropriate acidity, the synergistic effect originating from its double acidic sites and the promoting effect of water on the formation and transfer of protons. The Lewis acidic strength of IL played an important role in improving IL catalytic performance. A 100% conversion of 2-butene with 85.8% selectivity for C₈-alkylate was obtained under mild reaction conditions. The IL reusability was good because its alkyl sulfonic acid group being tethered covalently, its anion [Zn₂Cl₅]⁻ inertia to the active hydrogen, and its insolubility in the product. IL [HO₃S-(CH₂)₃-mim]Cl-ZnCl₂ had potential applicability in the benzene alkylation reaction with olefins and halohydrocarbons.

The alkylation reaction of isobutane with 2-butene to yield C₈-alkylates was performed using Brønsted–Lewis acidic ionic liquids (ILs) comprising various metal chlorides (ZnCl₂, FeCl₂, FeCl₃, CuCl₂, CuCl, and AlCl₃) on the anion.

Acidic ionic liquid based UiO-67 type MOFs: a stable and efficient heterogeneous catalyst for esterification

Acidic ionic liquid groups were introduced into the frameworks successfully and the resulting materials showed excellent activity.

Stability, Deactivation, and Regeneration of Chloroaluminate Ionic Liquid as Catalyst for Industrial C4 Alkylation

Alkylation of isobutane and 2-butene was carried out in a continuous unit using triethylamine hydrochloride (Et3NHCl)-aluminum chloride (AlCl3) ionic liquid (IL) as catalyst. The effects of impurities such as water, methanol, and diethyl ether on the stability of the catalytic properties and deactivation of the ionic liquid were studied in the continuous alkylation. In the Et3NHCl-2AlCl3 ionic liquid, only one half of the aluminum chloride could act as the active site. With a molar ratio of 1:1, the active aluminum chloride in the ionic liquid was deactivated by water by reaction or by diethyl ether through complexation while the complexation of aluminum chloride with two molecular proportions of methanol inactivated the active aluminum chloride in the ionic liquid. The deactivation of chloroaluminate ionic liquid was observed when the active aluminum chloride, i.e., one half of the total aluminum chloride in the ionic liquid, was consumed completely. The regeneration of the deactivated ionic liquid was also investigated and the catalytic activity could be recovered by means of replenishment with fresh aluminum chloride.

Lewis Acidic Ionic Liquids

Until very recently, the term Lewis acidic ionic liquids (ILs) was nearly synonymous with halometallate ILs, with a strong focus on chloroaluminate(III) systems. The first part of this review covers the historical context in which these were developed, speciation of a range of halometallate ionic liquids, attempts to quantify their Lewis acidity, and selected recent applications: in industrial alkylation processes, in supported systems (SILPs/SCILLs) and in inorganic synthesis. In the last decade, interesting alternatives to halometallate ILs have emerged, which can be divided into two sub-sections: (1) liquid coordination complexes (LCCs), still based on halometallate species, but less expensive and more diverse than halometallate ionic liquids, and (2) ILs with main-group Lewis acidic cations. The two following sections cover these new liquid Lewis acids, also highlighting speciation studies, Lewis acidity measurements, and applications.